Detalhes bibliográficos
| Ano de defesa: |
2023 |
| Autor(a) principal: |
Caminhas, Francielle Gonçalves
 |
| Orientador(a): |
Bueno, Guilherme Taitson Bueno
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| Banca de defesa: |
Bueno , Guilherme Taitson,
Cherem , Luis Felipe Soares,
Lima, Claudia Valeria de,
Zancopé , Márcio Henrique de Campos,
Leite, Marcos Esdras |
| Tipo de documento: |
Tese
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| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Universidade Federal de Goiás
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| Programa de Pós-Graduação: |
Programa de Pós-graduação em Geografia (IESA)
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| Departamento: |
Instituto de Estudos Socioambientais - IESA (RMG)
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| País: |
Brasil
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| Palavras-chave em Português: |
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| Palavras-chave em Inglês: |
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| Área do conhecimento CNPq: |
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| Link de acesso: |
http://repositorio.bc.ufg.br/tede/handle/tede/13408
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Resumo: |
The dynamic process of denudation renews and sculpts landscapes, reflecting the interplay between terrain lowering (downwearing) and the lateral retreat of slopes (backwearing). This interaction occurs through cycles of erosion (degradation) and deposition (aggradation), shaping the relief. This study aims to assess denudation, measured by cosmogenic nuclide beryllium-10, and its impact on the geomorphological evolution of the stepped surfaces in the Serra Geral region of Goiás, Brazil. The adopted methodology included: 1) geomorphological compartmentalization using morphometric analysis and remote sensing; 2) the selection of 20 representative hydrographic basins for the collection of fluvial channel sediments; 3) the collection of samples from surface formations at the top of a planation surface (Intermediate Surface); 4) the analysis of beryllium-10 (10Be) concentration in the collected materials, conducted at the ASTER AMS laboratory (CEREGE), Université Aix-Marseille, to determine the denudation rates of the sub-basins that flow into the Paranã and Tocantins rivers. Central to our hypothesis is the idea that a complex denudational dynamic shapes the evolution of the Serra Geral de Goiás and the incorporated surfaces, influenced by factors such as mass movements, fluvial incision, and aggradation zones. We identified four distinct regional compartments, characterized by differences in relief, pedological cover, and vegetation: (I) Central Plateau; (II) Intermediate Surface (divided into Remnant and Dissected); (III) Paranã Gap; and (IV) Escarpment, Mountainous Complex, and Relictual (Veadeiros Plateau; front of the Serra Geral Cuesta and relictual reliefs). The first three units were correlated with the South American surfaces, South American I, and South American II, according to Valadão (2009). Through the measurement of 10Be in fluvial sediments, it was observed that denudation rates are higher in basins linked to the escarpment of the Serra Geral, with a median rate of 87±9 m Myr-1 and variations from 43±4 to 196±61 m Myr-1 . This variation suggests greater instability in certain sectors, possibly due to the prevalence of mass movements and the remontant fluvial incision that forms festoons in the escarpment and captures watercourses from the São Francisco basin. The median denudation rate for the basins of the Intermediate Surface is 25±2 m Myr-1 , ranging from 11±1 to 44±4 m Myr-1 . The median denudation rate for the top of this surface was 11 m Myr-1 , suggesting greater stability in the planed sector, while the more aggressive hydrographic network of the Paranã rivers intensifies the excavation of the surface. For the Central Plateau, the estimated rate is 9±1 m Myr-1 . These data indicate a horizontal retreat of the escarpment to the east at a rate of 78±10 m Myr-1 (N-S extension). The vertical denudation difference between the Central Plateau and the Intermediate Surface is 16±3 m Myr-1 , indicating that the planation of the latter began between the Middle and Upper Miocene (8 to 18 Myr) and that the surfaces are reducing at different intensities. The Central Plateau presents an average excavation rate of 13±1 m Myr-1 , while the Intermediate Surface and the Paranã Gap show average rates of 32±1 m Myr-1 and 53±5 m Myr-1 , respectively. The consistent denudation, as evidenced by isotopic denudation rates, highlights the Intermediate Surface as a pediplain of prolonged exposure, which integrates into the regional geomorphological dynamics, with a median denudation rate of 25 meters per million years (m Myr-1 ), following the escarpment retreat. The stepped surfaces of this region are shaped by structural, climatic, and hydrogeological factors. Mass movements and wet areas are fundamental, as they influence denudation rates and contribute to the conservation of the geomorphological system. On surfaces with less incision and more resistant rocks, planation prevails, resulting in reduced denudation rates. On the other hand, on the Intermediate Surface, characterized by more aggressive incision and drainage, denudation rates are moderate to high. Fluvial erosion is directed by two main erosive fronts: one acts on the Intermediate Surface, under the control of the basal surface of the Paranã, and the other progresses over the plateaus from the escarpment, intensified by mass movements. The latter are crucial for the high denudation rates, while wet areas play a significant role in the aggradation process and sediment retention, acting as barriers to denudation on the Intermediate Surface and favoring geomorphological stability and river permanence. |
